1. Field of the Invention
The present invention relates to a pneumatic pruning hook with a telescopic shank, and more particularly to a pneumatic pruning hook with a telescopic shank that has an excellent airtight effect.
2. Description of Related Art
A conventional telescopic shank (6) of a pneumatic pruning hook in accordance with the prior art shown in FIG. 11 comprises an outer tube (62) and an inner tube (61) partially slidably received in the outer tube (62). A convey element (7) is longitudinally and separately received in the shank (6) for conveying compressed air. The convey element (7) includes an outer pipe (72) corresponding to the outer tube (62) of the shank (6) and an inner pipe (71) partially and slidably received in the outer pipe (72). The inner pipe (71) is moved with the inner tube (61) to adjacent a total length of the conventional pruning hook.
The inner pipe (71) is airtightly connected to the inner pipe (72) to prevent the compressed air from leaking between the inner pipe (71) and the outer pipe (72). A first O-ring (711) is mounted around one end of the inner pipe (711) and airtightly abuts an inner periphery of the outer pipe (72), and a second O-ring (721) is annularly mounted in the inner periphery of the outer pipe (72) and airtightly abuts an outer periphery of the inner pipe (71) to prevent the compressed air in the convey element (7) from leaking between the inner pipe (71) and the outer pipe (72).
However, the first O-ring (711) rubs against the inner periphery of the outer pipe (72) and the second O-ring (721) rubs against the outer periphery of the inner pipe (71) when adjusting the length of the shank (6) of the conventional pneumatic pruning hook. The airtight effect between the inner pipe (71) and the outer pipe (72) will be disappeared when the first O-ring (711) and the second O-ring (721) are worn out.
The present invention has arisen to mitigate and/or obviate the disadvantage of the conventional telescopic shank of a pneumatic pruning hook.